1. Field of the Invention
The present invention pertains to liquid treatment methods and devices, and more particularly to the separation of a lighter floating liquid on the top of a body of a second liquid. Herein, the invention will be described in connection with the separation of an oil component floating on a body of water although the invention may be used to separate other liquids, also.
2. Description of the Prior Art
Over the years, various arrangements have been proposed for removing oil from an oil/water mixture. One popular arrangement includes a rotatable drum, the majority of which is above the level of the oil/water mixture, but which establishes contact with the mixture's surface over a relatively small portion of the drum surface. As the drum rotates, oil floating on the surface of the mixture adheres to the drum and is maintained there due to the surface tension of the oil. Occasionally, costly chemicals must be added to the floating oil to enhance adhesion to the drum surface. A doctor blade scraps the surface of the drum, separating the oil film therefrom. In general, it has been found that this type of oil separation system lacks the separation efficiency necessary to provide an oil removal rate required in some production environments. While additional drums could be added if the tank holding the oil/water mixture were large enough, the cost of doing so is frequently prohibitive, especially considering the initial high investment cost required for even a single drum system. Further, systems of this type required frequent maintenance, thereby adding to the cost of operation.
The present invention will be described hereinafter in connection with a preferred use thereof which is with a washer for washing oil or grease from parts prior to a further treatment of the parts such as by spray painting. Often in the manufacture of products, particularly metal products, a coat of grease or oil remains on the product prior to its being spray painted and the part is washed by an aqueous alkaline spray. The spray rinses the oil coat from the product and the oil drops into an underlying tank in which the water is collected and pumped backed to spray nozzles which again spray the water against other products to remove any oil film thereon. This recirculation and cleansing with water continues, and after a while the body of water accumulates a substantial coating or film of oil on the surface of the water in the tank. When the oil becomes too deep, it has been removed by either the above-described rotatable drum or by a manual operation of opening a water inlet valve to admit more water into the tank to overflow the top layer of oil and water from the tank into an overflow gutter which directs the overflowing oil and water into collection drums. Often the overflow is 50% to 70% water and it is very costly to dispose of water. Because the oil spreads over the entire tank surface, a large quantity of oil may be present but spread into a thin film to be removed effectively by a manual overflow. The rotating roller apparatus described above is costly and is not that efficient.
Whatever is removed from the washer tank is processed as chemical or hazardous waste and, as such, at a high cost. Thus, where the quantity of water that is skimmed with the oil is equal to or greater than the quantity of oil, the storage cost may be doubled for storing water as a hazardous waste product. By substantially removing only oil with very little or no water, the hazardous waste product disposal can be reduced substantially.
Manifestly, the oil and water separation apparatus disclosed herein may be used with other apparatus than a washer booth and could be used, for example, to separate oil and water in a machine apparatus where large quantities of oil are recycled and reused in the process. Also, with suitable booms for containing oil slicks, the present invention may be used to remove floating oil spills or slicks from lakes, streams and oceans. The present invention provides a low cost and relatively maintenance-free system that removes substantially only oil, e.g. 98% to 99% oil from the surface of a body of water.